Banana armour

The skin of bananas in the fridge turns brown faster than those in a room, but the fruit is still edible.

I thought the browning was oxidation, but if so why does it happen faster in the cold?

While many fruits are stabilized by refrigeration, most tropical and subtropical fruits (bananas in particular) exhibit chill injury.
The ideal temperature for bananas is 13.3 C.
Below 10 C spoilage is accelerated by the release of enzymes and the skin can blacken overnight as the banana fruit and skin softens.